Regenerated cellulose sheet or film and method of making same



Patented Dec. 17, 1935 REGENERATED CELLULOSE SHEET on FILM' AND METHODor MAKING SAME;

Daniel W. Losee, East Patchogue, N. Y.,' assignor to Johnson-LoseeCorporation, Long Island City, N. Y., a corporation of New YorkApplication August 1, 1933, Serial No. 683,229 ,7

12 Claims.

material whereby it will be adapted for a wider I variety of uses, asfor .example for photographic purposes. It is also an object of myinvention to produce a fire-proofor fire-resisting film .or sheet byemploying a fire-proofing agent which heretofore has not been used forthis purpose. It is also an object to produce film or sheets which arenot only superior to existing types but which can be produced at asaving in cost. One means by which I achieve a lower cost'of manufactureis by the use of lower grades of cellulosic material, as

for example cotton seed hulls or husks which I.

have discovered can, by proper-treatment, be used to producea'regenerated cellulose which has exceptional qualities for the presentpurposes. As is well known, regenerated cellulose sheets are affected bymoisture and heretofore, it has been proposed to coat such sheets with alacquer containing waxes. I have discovered that by utilizing theincrustations or wax-like or resinous substances naturally present inthe cotton fiber or cotton hulls for example, it is possible to dispenseentirely with the use of Wax in the coating material. Because of theabsenceof wax on the outer surface of the film or sheet, the coating isnot as sensitive to higher temperatures, especially in the presence ofwater vapors, and a better surface is aiforded for the adherence ofother films such as gelatine containing a light sensitive emulsion. v

In carrying out my invention, after the celluresult is accomplished Iascribethe superior ac- 45 tion of the cuprammonium process over otherssuch as theviscose process, for example, to the fact that the processused does not decompose or remove substantially the natural waxes andresins in thecellulose fiber. In my use of the cupram- 50 monium processI have found it desirable to make certain changes from such processes asheretofore practiced which I believe to be novel and tobe responsible inpart for my superior results. A further advantage of the use of theimproved cu- II prammonium process is that the cellulose solutions arerelatively stable and may be kept for longperiods of time, incontrast tothe viscose method, for example, in which the sodium Xanthate cellulosesolution must be aged or ripened with great exactness or otherwise thesheets 5 formed therefrom are of inferior quality. Furthermore, in thecuprammonium process as I employ it, the solution is effected'with greatrapidity and also the recovery of the starting materials, as for examplethe ammonia and the copper salts, 10 is relatively complete,therebymaking for very economicaloperation. f v

The cellulose containing the correct amount (say, at least, 3% thereof)of the natural incrustations having been brought intosolution, the 15next-step is to cast the film or sheets. This may be done byknown means,after which the copper and ammonia are recovered from the casteellulosicmaterial. In adapting the cuprammonium process for my purposeI have devised special con- 20 ditions. under which the coagulation ofthe cellulose takes place, all of which will be disclosed in greaterdetail hereinafter and which contribute to the successful operation ofthe process. g 7

After the film has been regenerated .byremoving the ammoniaand copperfrom the cellulose, the film isimpregnated with the fire-proofing agentand then dried. While regenerated cellulose films are not explosivelyinflammable as is celluloid yet they burn with suflicient ease to con-30 stitute a fire hazard, particularly when used as the base for motionpicture film. Moreoven forother purposes even as awrappingmaterial theinflammability of the regenerated cellulose film is considerable so thatthe fire-proofing of this material is'a matter of considerable value andimportance. Becauseof its ease in,applying,;it has been my endeavor toprovide a water soluble fireproofer which, however, would in no wiseimpair the transparency of the film or sheet and yet have the necessaryeffectiveness. After much experimentation I have discovered the ureaphosphates,

. preferably the orthophosphates, to be extremely well suited for thepurpose and to be not only dicated, it is then coated with a suitablelacquer which may be of a relatively simple composition consisting of asolvent, 9. cellulose derivative base, as for example cellulose nitrate,ands. guniggorg' As a solvent I- prefer resin such as gum dammar. to usea mixture of a major portion of acetone and a minor portion of amylacetate or an equivalent ,high boiler but. yarious other}: solvents maybe used and I do not-regardthe, selection of particular solvents ascritical, regardbeinghad to standard practice in the cellulose lacquerart. The use of waxes in the lacquer isunnecessary.

The retention of fronr.3 to 5% ofm'oisture also assists in causing theco -t ng to "adhere to the cellulose base. My explanation for this is asfollows: when thefllm contains a fewper cent of, moisture, its surfaceis somewhat rough and of open texture which permits the lacquer topenetrate into the fiber and thus to'adhere more firmly. When part ofthis moisture escapes along;

with the lacquer solvents during the" drying oprationithe surfac'eparticles contract somewhat, thereby strengthening the union" of thelacquer and regenerated cellulose. Starting with a film. containing fromthree to five per cent moisture, it is found that the moisture contentwill fall approximately one percent during the drying of the coating.One advantage of 'the improved coated film is that the moisture can bereduced to as little astwo per cent without impairing substantially itsflexibility, this result being con- .sidered due in large part to thecombined plasticiz'ing qualities of the urea phosphate and the.

natural waxes; The ability of the improved film of maintaining itsflexibility with such a low moisture content permits it to be used undera wide variety of climaticf conditions without the use of specialprecautions. The amount of moisture'in the regenerated film-beforelacquering is susceptible to a somewhat greater value than five percent, particularly if more severe drying conditions are used in thedrying step following the application of the lacquer. If, however, thecontent of moisture be too great the factor of shrinkage of the filmupon drying will'be inconvenient. The amount; of moisture in the filmvaries somewhat with atmospheric conditions, but such variation asnormally occurs is insumcient to interfere with'the intended uses of thefilm.

A further factor which I believe promotes this adherence is that thenaturally present waxes and resins act as abinder for the cellulosederivative -coating since they are both bound to the cellulose basematerial and are soluble in the cellulose derivative coating. ,7 r

The film is water resistant to the extent that it can be used forphotographic. purposes and developed without swelling E01. shrinking toan amount which'will interfere with the proper use of the film in theprojector. parent, fiexible,,strong, fire-proof, and colorless, andretains these qualitieswhen used for photographic purposes.

In the annexed drawing I have shown a diagram or so-called flow sheet ofa specific example of the process illustrative'of 'my invention,.of

making a water-proof film from cotton seed hulls.

The following is a detailed description of the example outlined in theflow sheet:

Preparation of fiber Caustic .soda treatment-Cotton seed hulls (presscake) containing sixty-five to seventy per cent cellulose fiber, areboiled for .twohours with a two per cent caustic soda solution atfivepounds f hot water to restore the original volume. one part ofsodium hypochlorite solution is diluted Itis highly transpressure, usingone gallon of the solution. to one poundof cottonseed hulls. .Thesolimmaterial is then's'eparatedfrom theused liquor, washed untilthewashings are colorless or nearly so, and the fibers then centrifuged.The fibers thus 5 treated are then subjected to a secondsoda boilfortonerhllt solution, of two percent caustic soda. The used liquor fromthis step is preferably used in the first soda boil. The

with seve'n'to nine parts of water according to l the grade of rawmaterial and then employed 25 in the amount of one gallon of the dilutedliquor to one pound of cotton fiber. The bleaching operation is'carried.out at a moderate temperature preferably not exceeding 40 C. andcontinued for about three hours.

Washing and drying.-When the fiber has acquired a bluish-whiteappearance it is washed in wateruntil it is free from odor andis withoutalkaline reaction. This washing may be fol-- lowed bya dilutehydrochloric acid wash for the 5 purpose of whitening thev product stillfurther by removing the iron that may be present. If possi-. ble, theacid-wash should be avoided as the acid decomposes certain naturalmagnesium soaps comprising the natural 'incrustations, ,which 40 soapsare preferably retained. The acid wash however seems .to resultinthefiber keeping longer in storage. If it is intended to store thefiber it is dried at60 C. until the moisture content is reduced to about5%; if, however, the fiber is to be dissolved, a greater amount ofmoisture may be left in and dryingwlth heat omitted. Thefiber containingmore or,less wateris now ready for the step of solution making. The useof the still 'wet cellulosefor solution jnaking is 5 preferred since itis found that the drying of the fibers hinders the complete re-swellingthereof during the subsequent treatment.

It will be understood that the treatment thus far described acts topreserve the necessary quan- 1 tity of the insoluble incrustations inthe fiber.

v Dissolving the cellulose I r The prepared 'cellulose preferablyuntitled from the purifyin'g stepsis first drenched with ammo nia of 26B., preferably in the proportion of 100 poundsof cellulose (dry weight)to 333% pounds of ammonia. (-26; B.) "whereupon 78 pounds copperhydroxide,*Cu(0H):=and 24%"gallons of water are added. By the use ofthis method a relatively concentrated solution of cellulose, e. g., 16%,may be obtained. Instead, however, of proceeding'in the mannerdescribed, even better results are obtained'by the use of the followingmethodfz" f' I jE-S J 25 pounds copper sulphate CuSO4.5H2O are dissolvedin 45 pounds of ammoniumhydroxide of 26 B. whereupon 12 pounds of thepurified cotton fiber are added. Then eight poundssodium hydroxide in 15pounds ofuwaterare added,

, r "9,025,000 whereupon solution of the fiber takes place'at washedonce, such solution containingusually about 16% of cellulose. Thissolution is then filteredin a q filter'press or through. sandand passedto a store 7 age tank. Bubbles are removed either by allow- 1' ing thesolution to stand or by application ofslightvacuum. It will be notedthat this last described method of dissolving the cotton has theadvantage of not employing copper V hydroxide which it is necessary toprepare by reaction of a soluble copper salt, usually the sulphate, withcaustic soda followed by filtration of .the .cu'pric, hydroxide, anoperation of some difiiculty. While not absolutely necesasry, somewhatbetter results are achieved in the soda 'boils'by the presence ofcatalysts" which are prepared from sea salt preferably as follows: I u

Fz'istv'nethoi-IO grams sea salt aredissolved I in 75 'cc. HNO:solution, evaporated until nearly dry, then cooled and allowed tocrystallize, the crystals filtered off and slightly washed.

' Second method-Same procedure is followed, exceptthat sulphuric acid isused instead of ni- 'tric acid and the calcium sulphate formed isfiltered ofi before evaporation.

Preferably 25 grams per 100 pounds of cotton u of the product of method#1 are added during the I .first soda boil, and grams per 100.po'unds'0f cotton or the product of method #2 are'added during thesecond soda boil. 4 I

I casting The film is cast using known apparatus prob; erably consistingof a slowly rotating casting wheel or endless belt on whichthe'cellulose solution is spread using an orifice of known width. Afterthe liquid has flowed out upon the wheel'- in this manner, continuedrotation 01' the wheel",

carries the freshly formed film into the coagulat-V ing bath containing,for example, from to partscausticsoda per 100 parts of water; ,Immersionin this bath is maintained for approximately fourminutes at roomtemperature, i. e.,

up to 30 C., after which that portion of the wheel containing the'coagulated film leaves thecoagulating bath, whereupon the film'isstrong enough to be stripped from the wheel. When using a casting wheelthe surface upon which the solution is poured has been previously wetwith thecoagulating solution so that coagulation of the portion'of thefilm next to the wheel begins at.

once and the filmis prevented from sticking to the wheel. The film isthen conveyed to an aging. bath of a strength which may be the sam asthat of the coagulating bath and maintained a a tem-,

perat'ure from toj'65. C.. The time ofimmersion in this bathvaries'chiefiy withthe thickness of the film. By casting the film at acomparatively low temperature, the formation of air bubbles in the filmis avoided, while by the use of the sub.-- sequent higher temperaturethe coagulatingtime, remains low-and the flexible features of the ulti-.mate product are advanced. 1 Thus, the aging of the film of .004 inchultimate thickness maybe...

completedwithin twentylminutes from the timeof. casting. The filmisthen'washed with cold water, for which five minutesisusuallysufllcient time, and the copper removed by the use of 1preferablyan acid solution consisting of 5 B, sulphuric acid... A slightquantity of seasalt. maybe added to the acid for the purpose ofaccelerating the decoloration. The removal of the cop-. per from thefilm is complete when the last trace.

of color is removed.v Following'thisthe film is ing doesnot appearto becritical so that a variety desirable.

The film is'now passed through ante-proofing bath consistingfbfasolution of approximately bath" the film requires about. three i minutesfor impregnation; "Ththus impregnated film is now dried" at'ajtemperature preferably not exceeding from 3 f to" 5% '.of Wfltlf: Theregenerated cellu-; lose film thus formed, containing'from 1.8 to 2%ofthefire-proofer, dependingjupon the thickness I j u of the fillm', isnow ready for the coating step.

gamma this purpose preferably the renewing lacquer is used; acetonel75pounds, amyl acetate 15 I. f

, pounds, 'pyroxyli'n 3 pounds, gum laminar or I other resin 3 pounds."This'solution' is placed lna bath through which the film is caused "topass after which the'thus 'coated film is dried forfjap-u goximatelythree mimitesv at amoderate heat',-say

o g. f?

thickness can beorrthe order of-.001 to:.002-or higherjup to:1 12/l0Q0", .-depending.on-the in-"sd I tended use. 'Ihe pyroxyiiri coatingmaytvary from'.0001 to .OOlf'; preferably being used thinner on thewrapping material than on the "photo- 5 graphic 'filmiiForphotographicpurposestheit illrn is now ready for-the gelatine light, sensitive'emulsionpreceded 'by'the 'application 'or-theiso- I H u up Iiscustoma'ry U in the "artfof; coating film with'photographic calledsub-stratum, if necessary, as

emulsiom 1 Recooery of materialsand aging f-tanks", and. is removed bymeans :0! a suction fan. (the tanks being closed) and recovered inaccordance withthe standard ammonia 7 recovery practicewFor the purposeof recovering 5 u the copper the decolorizingbath, .after 'ithasbecomeexhausted, is preferably filtered and pumped i into tankswhere. the; copper is. precipitated as copper hydroxide withcausticsoda. This ,puts

.. thej-copperintheform in which it: is to be used, in

the firs'trsolution methodabove given, namely, as

copper hydroxide iwhereathe copper isto be used in the former sulphate,asin thesecond method ,given, the sulphuric "acidlsolution con.-

- taining the copperis simply evaporated until the coppersulphatecrystallizesoutl Because of thenatural 'water-proof 'qualities.of i the rege erated celluloseflim'containing there sidual waxes and,re'sins, the-nature of the coatof types of lacquer may be employedqBecause of its cheapnessI' prefer to. use a lacquer having a pyroxylinbase andcontai n asimple gum, but other cellulose derivativess'uch asvarious types of the cellulose ethe'rs may-be used witha.suitablegumjifdesired. In lieu or gum dammar Ijmay] usegum. copa l,mastic, 'estergum, or

. various ofgrthe synthetic resins. For some 1purposes it is possible toapplya coatingcontaining I waxes to the-film if desired,fbut I havefound the I use of su ch-va:.wax containing".coating 'to beun Myimproved filmis not only therebyadapting it for use as a wrapp ns matrial, but is further unaffected by water to such in cold water foraperiod on theorderof I i I f For 'photographie purposestheregeneratedcellulosebasewillbe'of'.00inchthickness approxi fi mately,whileforjuseasawrapping material the l Y .,..-4 o The ammoniaisgivenQofl in the coagulating here firmly to the an extent that it isadapted for use asfa base for photographic film, as for example, motionpicture film. Heretofore many attempts have been made y toutilizeregenerated cellulose as the base of motion picture fihn but theseattempts have notbeen successful.- I the distortion undergone by theregenerated cellulose upon being wetted in the developing, wash- .ingand fixing baths.

One reason for this non-successis Another reason has been moistureproo'f coating to adbase. ,In cases .where. the re-- has beensuccessfully waterthe failure of the generated cellulose I proofed forthe purposes of makings. wrapping 1 to the absence of material, suchsheets have beenunsuited as a base forphotographic film because ofinability ofthe gelatine emulsion to adhere thereto. Owing wax in thecoating of my it can be coated with a light, Sensitive gelatme emulsionof silver salts by usual methods without 20 difficulty. Moreover,because of the presence of thefire-proofer, the improved Ifilmisnon-inflam- .mable. Application or heat to the film causeslit to, charrather than to burn, and, furthermore,

1 :such charring takes place withoutliduefaction of r e by theburning ofnitrate and acetate films; .30: 1

. maybe madejfrom" the details given and satisthe film such as occurswhen acetate'film is heat ed. Furthermore, the; gases combustion arerelatively non -toxi'c"in contras to the poisonous characterof the gasesproduced In carrying out the process varlous departures factory resultsproduced, Thus, .whilebecause of their cheapnes's and peculiaradaptability for the purpose I prefer the use of cotton seed hulls,.cot-

-3 ton linters or other cotton fibers may also'be used the f preliminarytreatment of l these slightly where necessary.-

fan I haveby the higher percentageoficellulosegiven, the I P m narysodaiboils will be less severeand one ymaybeused 7 The quantity'ofthe,atural incrustations .in ordinarycotton fibers var'ying as'a rule frorn3 to 5% is sufficient to impart the desired moistureproofing andflexible qualities to the film. Further, while for most purposes Iprefeito fireproof the film as described; yet for uses where thecombustibility of the. regenerated filmvv is. without consequence, :thefire-proofing stepgmay be omitted. I I

- Thusfar I have"found ureaphosphate to be greatly superior to allother. water, soluble fireproofing salts, i particularly :ammoniumsalts,"

which, to my knowledge, have heretofore been proposed; Thus'I havefoundthat such ammonium salts asghaye been used for fire-proofingvariousmaterials crystallize too easily-whenapplied to the film either at thetime the film is dried 'or else after a period of a few days or weeks,Other ammonium salts otherwise suitedfor fireproofing have the effect ofrendering the film brittle and-dark'after a'short period. Urea phosphate while having fire-proofing qualities equal 01" superior tothose'o'f the flre-proofers heretofore proposed'hasnone of thedisadvantages of be employed in ve'ry dilute solutions, 1., e}, as lowas 3 *while: yielding satisfactory results. Moreover, it-also acts alongwiththe'naturally 1 present incrustationaas a, plasticizer in he film.

In addition to urea phosphate,yIfhave also found' that's'odiumthiosulfate functions wellbut this lution is added, is notclaim'edherein but is the alcohols (waxes) such as gossyphyl alcohol andmontanyl alcohol together with lesser quantities produced by the a 1proved regenerated and lacquered cellulose sheets i now manufactured byothers. Thus, sheets of my effect of water as drops at room temperature(u to 40 C.) for a periodof at least forty-eight ho (without anynoticeable deterioration or separa ftion of the lacquer coatings. In thecase of the g has penetrated the lacquer coating, and to the substancehas the drawback of giving rise to very disagreeableodors when the mailsdecomposed by heat. l

' I have found the-solution-of the cellulose by means of thecuprammonium process to be of particular value because it preservesinthe cellulose the necessary quantity ,of the natural injcrustations, butI may use anyyother method of solution solong as these incrustations aresumciently retained to function in the desired manner.' 1

v The process of dissolving the cellulose by first dissolving a coppersalt in ammonia and then. adding the cotton, after which a caustic sodasosubject of a separate application filedby Werner Kleinicke, on August1st, 1933, now Patent 1,972,098 issued Sept. 4, 1934.

It is understood that the natural incrustations, of the cotton fibers,both'seeds andhulls, owe their wax-like properties chiefly to certainhigher of acid esters, glycols, etc. They further include magnesiumsoapsof certain fatty acids, which soaps sometimes amount to /2 of 1% ofthe weight of the cotton in the untreated'state. The exact compositionof the incrustations is not known,

' however, and undoubtedly varieswith different cottons. By the termincrustation in the claims it is intended to cover these wax-like orother insoluble compounds which, are found naturally occurring in cottonand fibers of like nature and which contribute in the final product tothe I water-proofing qualities and flexibility thereof,

irrespective of the particular chemical composition of suchincrustations or the mannerbf their occurrence in" the fiber.

' By water-proof I mean the ability of my im- "improved coated materialof the thickness of wrapping material, i. e. of approximately onethousandth of an inch or'more have withstood the prior art, so-calledmoisture-proof sheets. used j for wrapping cigarettes, .for example,show marked deterioration aftercontact with a drop 5 of water over aperiod of an hour orless. This deterioration manifests. itself by aswelling or blistering of the sheet," the cause. of which is theswelling of the cellulose base dueto water which presenceof the excessof water under the coating after the saturation of the sbasaf Eitherthis swelling of the base, or its distortion incident upon 'thesubsequent drying thereof, results, in most 6 cases, in the rupture ofthe lacquer coatings on both'sides and hence in the total destruction ofd {the moisture-proof quality of the sheet. In the such'proposedfire-pr'oofer and in addition may case of applicants product, on theother hand, such blistering does not develop even after prolongedcontact withtd'rops of water, and this action may be explained bythefact that not only does. applicants regenerated cellulosebase havegreater. water resistant qualitiesby reason of the retainedincrustations but the presence of such aoaaooo Y 5 incrustations causesa much firmer bond between the base and the lacquer coatings.

The complete process describing the various steps set forth is believedto produce a most effective waterproof film for use as a base forphotographic film or for other purposes. As will be apparent, however,some of the steps of the proc-' ess described are of utilityindependently of the complete process. For instance, the preparation ofthe cellulose while retaining in it some or all of the non-solubleincrustations possesses potential advantages for other purposes than.the manufacture of film, such for example for the preparation of textilefibers. The improved methods of preparing cuprammoniumsolutions ofcellulose are also capable of employment in the manufacture of rayon, orfor other purposes. The method of fire-proofing and the use of thefire-proofing agent specified, urea phosphate, is also applicable to thefire-proofing of products of many kinds.

1. An article of manufacture comprising a substantially transparentsheet or film of regenerated cotton cellulose combined with a waterresistant,

transparent, flexible, non-tackycoating, said regenerated cellulosecontaining sufiicient of the natural incrustations so as to render thearticle water-proof without the presence of added waxes in the coating.

2. The article of manufacture according to claim 1 in which the naturalincrustations are left in the fiber to the extent of at least .3 of 1%.

thereof.

3. The method of making a transparent, flexible, water-resistant sheetor film which comprises alkalizing rav, cotton cellulose material andthen bleaching the same, such steps being carried to a point where thematerial is'rendered colorless but so as to leave substantiallyunattacked part of the naturally occurring incrustations, dissolving thecellulose so prepared in a cuprarnmonium solution, and then casting thefilm, coagulating transparent, flexible, non-tacky coating, saidrgenerated cellulose containing sufficient of ith e naturalcottonincrustations so as to render' the article water-proof without thepresence of added waxes in the coating.

5. The method according to claim 3 in which cellulose the film beforecoating contains from 3 to 5% of water. I

6. The method of manufacturing transparent films or sheets of cellulosecomprising purifying V raw cotton fiber so as to leave a substantialproportion of the natural incrustations therein, dissolving same by thecuprammonium method,

forming the mixture into transparent, regenerated cellulose sheets,impregnating the cellulose sheet with an aqueous solution of a watersoluble, 10

transparent fire-proofer, drying and then looking in. the fire-prooferby coating the dried sheet containing the proper amount of moisture witha suitable transparent, fiexible, water-resistant 8. An article ofmanufacture comprising a sheet 20 t or film of regenerated celluloseimpregnated with urea phosphate and containing from 3 to 5% of moistureand having a water resistant, transparent, flexible, non-tacky coating.1

9. In the art of making cellulose sheets, th 25 method of preparingcotton seed hulls for solution which consists in boiling the hulls inapproximately 2% of alkali under slight super-atmospheric pressurenotexceeding six pounds for about two hours, then washing, repeating the 3alkali boil for a shorter time and then bleaching to the point where thecolor disappears and then dissolving the thus treated cellulose incuprammonium solution whereby a substantial portion of" the naturalincrustations of the cellulose fiber is 35 retained by. said solution;

10. The method of rendering cellulose articles fire-proof which consistsin impregnating them with urea phosphate.

11. The method of increasing the water-resist ant qualities ofregenerated cellulose which com-1 prises so treating the cellulose as topurify and bleach same while retaining a portion of the naturalincrustations of the cellulose fiber, dissolving the so treatedcellulose so as to retain a 45 substantial portion of the incrustations,casting the dissolved cellulose and regenerating same, whereby suchregenerated cellulose contains sufficient of the said incrustations soas to render the cellulose water-proof upon coating same with a simplepyroxylin coating containing no waxes. 12. An article of manufacturecomprising a sheet or film of regenerated cotton cellulose combined witha water resistant, transparent, flexible, non-tacky coating, saidregenerated cellulose con- 5 taining sufiicient of the 'naturalincrustations s0 as to render the article water-proof withoutthepresence of added waxes in the coating, said article containing ureaphosphate as a fire-proofer.

DANIEL W. LOSEE.

